The purpose of this proposed research is to develop a sophisticated membrane system into a hemodialysis unit which will function in a mode similar to a biological kidney. This artificial kidney will produce a true urine-product. This goal will be accomplished by utilizing: 1) the process of chemical etching for forming staged, tortuous microcapillaries (10-250 micron diameter). These capillaries have been proven to reduce boundary layer effects, maximize the ratio of area of membrane to prime volume and reduce clotting; 2) piezodialysis yields (reversibly) piezoosmosis and dialysis yields (reversibly) osmosis to remove salts and water from the ultrafiltrate in order to concentrate the organic solutes; hence, a true urine-product will formed. The salt and water will be returned to the patient after passing through absorbants; hence the dialysate wash will be totally obviated; 3) experiments are proposed to determine the relationships between solute and solvent transport and hydrostatic and osmotic pressure for blood- membrane-solution systems and other biological fluids; these experiments will have important clinical value for understanding the disequilibrium syndrome associated with hemodialysis. Mosaic membranes will be used as a model for studying molecular transport in solute concentrations equivalent to biological solutions. These experiments will completely evaluate the mosaic membranes from the standpoint of irreversible thermodynamics.